Advanceable mining support arrangement



June 1, 1965 w. VETTER ADVANCEABLE MINING SUPPORT ARRANGEMENT 2Sheets-Sheet 1 Filed April 10, 1962 June 1, 1965 w. VETTER 3, 7

ADVANCEABLE MINING SUPPORT ARRANGEMENT Filed April 10, 1962 2Sheets-Sheet 2 l|llIIlllllllllllllllllllllll1||llllllllllllllllllllllliill| IlllllHHIIIHIIIIIHIIHIIIIII HIHHUI M IIHW H HIHIIIIIIIIIIIIHHIIIIIIH ullllllllllllltlli l i I n IHHIHIH 1H;

:IIIIIII HIM //vv NTOR eVre United States Patent G 33,072 15 Claims.(Cl. 61-45) The present invention relates to an advanceable miningsupport arrangement with adjustable prop means for engaging the mineceiling and mine floor, and more particularly to such an arrangementhaving a moving means capable of forward and rearward movementinterconnected with four prop means formingtwo diagonally connected propsets for alternate actuation in the moving direction.

In mining operations carried on for the extraction of mineral from amine face, it is known to use an advanceable prop frame arrangementwhich serves to support the overhead seam or mine ceiling. Thesearrangements are known as walking frames or advancing frames.Specifically, for example, one proposal has been to combine a pair ofprop frames into a common unit, with the prop pairs positioned parallelwith respect to one another in such a manner that the moving means willalternately shift one frame in the forward direction and thereafter theother frame. For this purpose, a double acting pistoncylinderarrangement is commonly employed with one prop frame being connected formovement with the cylinder and the other prop frame connected formovement with the piston. The advancing is actually achieved by reasonof the fact that one frame is placed into engage ment with the minefloor and mine ceiling via the pit props while the other frame isdisengaged for movement in the desired direction, the engaging propframe contributing the desired leverage. Once the advance has takenplace in this manner, the disengaged frame is engaged with the mineceiling and mine floor so that the engaged frame may be disengaged foradvancing in its turn.

A further proposal has been made in which the two frames of each pairare alternately moved in the forward direction by means of a separatelyassigned moving means, i.e., a separate piston-cylinder arrangement. Inthis instance, the disengaged frame is moved forward by its ownpiston-cylinder arrangement, and thereafter this frame is placed inengagement and the already engaged frame is disengaged and moved inforward direction by reason of its own piston-cylinder arrangement.

An even further improvement which has been proposed is one in which apiston-cylinder arrangement is provided which is connected with therespective prop frames so that transverse or diagonal movements may becarried out between the piston-cylinder arrangement and the prop frames,otherwise normally parallel to the advancing direction. In the case ofthese prop frames, guide rods are provided with respect to the propswhereby during the advancing a flat circular arc may be executed tochange the disposition of the prop frames with respect to thelongitudinal direction of the piston-cylinder arrangement.

All of the aforementioned types of advancing frame arrangements whichuse piston-cylinder arrangements as moving means suffer from thedisadvantage that during the advancing of one frame with respect to theother, the distance apart of the prop means in general increases .bymore than twofold. Although support of the overhead seam or ceilingwithin the range of working or advancing is absent for only a short timeinterval, due to the fact i present. Specifically, where aplural. numberof parallel 3,186,179 Patented June 1,1965

pairs of frames are used along a mine face, generally the prop frame onone side of every pair is disengaged simultaneously for advancement, andthen the prop frame on the other side. The total lack of support alongthe entirety of the mine face thus signifies a safety consideration inmining operations.

It is an object of the present invention to overcome the foregoingdrawbacks and to provide an advanceable mining support arrangement withadjustable prop means for engaging the mine ceiling and mine floor whichpermits a more equal distribution of the supporting forces over the areaoccupied by the arrangement so as to avoid the danger of collapse of themine ceiling. 7

Other and further objects of the invention will become apparent from astudy of the within specification and ac companying drawings in which:

FIG. 1 is a schematic top view, partially in section, illustrating oneembodiment of the invention and indicating in phantom the alternateposition for two of the mine props present,

FIG. 2 is a schematic partial sectional view taken along the line AA ofFIG. 1,

FIG. 3 is a schematic partial side elevation view of the embodimentshown in FIG. 1,

FIG. 4 is a schema-tic partial top view of the linkage of the embodimentof FIG. 3 shown in extended position,

FIG. 5 and FIG. 6 represent schematic top views of a plurality of pairsof mining support frame arrangements representing the prior art and thepresent invention respectively.

It has been found in accordance with the present invention that animproved advanceable mining support arrangement with adjustable pit propmeansfor engaging the mine ceiling and mine floor may be provided, saidarrangement comprising moving means having a forward and a rearward end,first prop means positioned adjacent said forward end on one side of themoving means, and second prop means positioned adjacent the rearward endon the opposite side of the moving means, the first and second propmeans together forming a prop set and being connected with the movingmeans for simultaneous forward and rearward movement, and third propmeans positioned adjacent the forward end on said opposite side of themoving means, and fourth prop means positioned adjacent the rearward endon said one side of the moving means, the third and fourth prop meanstogether forming a prop set and being connected with the moving meansfor simultaneous forward and rearward movement alternately with themovement of the first and second prop means.

Preferably, the moving means includes a'double-acting piston-cylinderarrangement with the piston connected with one of the prop sets forsimultaneous movement and the coacting cylinder connected with the otherof the prop sets for simultaneous movement alternately with the movementof the first-mentioned prop set.

In accordance with the preferred embodiment, the prop means :of one setare interconnected by a first diagonal cross-element and the props ofthe other set are interconnected by a second diagonal cross-elementoverlying the first cross-element. The adjacent cross-portions of thecross-elements are disposed in sliding abutment with each other.Specifically, the piston-cylinder arrangement includes a double-endedcylinder and a double-ended piston rod extending through thecorresponding ends of the cylinder, the piston and cylinderbeingarranged for actuation in forward and rearward direction with respect toone another. The cylinder is longitudinally'disposed be tween the firstandfourth prop means on one side and the third and second prop means onthe'opposite side, such that the cylinder is fixedly secured to thecross-portion of 3 one of the diagonal cross-elements to move thecorresponding prop set while the piston rod is connected at each endwith a corresponding prop means of the remaining set to move that setalternately with the movement of the cylinder.

Notably, the axis of the cylinder longitudinally bisects thecross-portions of the diagonal cross-elements and the cylinder isfixedly secured to the top side of the overlying diagonal cross-element.This is achieved by a clamp strap extending in the direction of andbeing substantially coextensively secured to the'cross-element top side,the clamp strap having an intermediate upward arcuate portion 'definingwith the corresponding portion of the cross-element a seating channelextending in the longitudinal direction. This channel serves forreceiving at least a portion of the cylinder in fixed relation thereat.

Preferably, the corresponding portion of the overlying cross-element isslightly downwardly arcuately depressed in the longitudinal direction toform a guide rail on the under side of the cross-element and in turn thecorresponding portion of the cross-element underlying the overlyingcross-element is also slightly downward arcuately depressed in thelongitudinal direction whereby to form a corresponding guide track onthe upper side thereof. In this manner, sliding abutment between thecrosselements may be carried out in coacting guiding relation.

Each prop means is provided with a lower end and an upper end, thecross-elements and piston rod being connected to the prop means at thecorresponding lower ends. The prop means are also each provided with anoverhead supporting cap at the upper end, the supporting cap extendingin longitudinal direction as well. The lower end of each prop means isprovided with a prop base in which the lower end of the prop meansiseffectively .seated. The prop ends of both of the prop sets aredesirably displaceably seated in the corresponding prop base so that thebase may execute slight pivotal displacement about the end as pivotpoint.

In accordance with a particular feature of the invention, the first andfourth prop means on the same side of the moving means orpiston-cylinder arrangement are longitudinally interconnected at theirtop ends through their corresponding overhead caps by an overhead capadjustable length linkage, while the third and second prop means on theopposite side of the moving means or piston-cylinder arrangement arealso longitudinally interconnected at their top ends through theircorresponding overhead caps by an overhead cap adjustable lengthlinkage. These linkages are adjustably dimensioned for permitting theset, including the first and second prop means, to move forward in thelongitudinal direction of advance while the set, including the third andfourth prop means, is stationary, so that the cap linkage between thefirst and fourth prop means will increase in length while the caplinkage between the third and second prop means will decrease in length.Alternately, the dimensioning is such that the set, including the thirdand fourth prop means, is permitted to move forward in the longitudinaldirection of advance while the set, including the first and second propmeans is stationary, so that the cap linkage between the first andfourth prop means will decrease in length while the cap linkage betweenthe third and second prop means will increase in length.

More specifically, each cap linkage includes middle linkage bar meanspivotally connected at each bar end to lateral linkage bar means. Eachlateral linkage bar means, in turn, is separately pivotally connected tothe substantially outermost point of the corresponding over-headsupporting cap. The middle linkage bar means and the lateral linkage barmeans permit extension and retraction in length of the correspondinglinkage in longitudinal direction in coaction with the forward movementof the prop sets.

Significantly, the sum of the distances between the center point of eachof the two prop means interconnected by one of the cap linkages and therespective outermost point of the corresponding overhead supporting captherefor which is pivotally connected to the said one cap linkage isshorter than the sum of the distances between the center point of eachof the remaining two prop means interconnected by the other of the caplinkages and the respective outermost point of the correspondingoverhead supporting cap therefor which is pivotally connected to thesaidother cap linkage. Such shorter distance is actually shorter by anincrement equal to at most the maximum amplitude stroke of the piston inthe cylinder.

It is most advantageous to provide the diagonal crosselements asresilient fiat leaf spring members and to provide resilient flat leafspring connectors between the piston rod and the corresponding propmeans connected therewith, in order to provide a sufficiently resilientarrangement capable of accommodating uneven surfaces in the mine floorand mine ceiling without undue stress on the working parts.

Furthermore, prop means are provided as hydraulically operated pit propmeans, i.e., hydraulic jacks, and the piston-cylinder arrangement mayalso be hydraulically actuated. While hydraulic fluid, such as hydraulicoil, is often used to actuate the piston-cylinder arrangement,compressed air may also be used for this purpose as is well known in theart.

The advantages of the mining prop arrangement in accordance with theinvention are readily appreciated from the fact that a more uniformsupport of the overhead seam during the advancing of the arrangementwill be achieved as well as a greater stability under load of thearrangement due to the cross-wise or diagonal connecting disposition ofthe props in each frame, albeit that the overlying supporting capsremain parallel to one another in the longitudinal direction of advance.

Referring to the drawing, FIG. 1 shows an advanceable -mining supportarrangement with adjustable pit props for engaging the mine ceiling andmine floor, the overhead supporting caps being omitted for facility inunderstanding the particular construction involved. Props 1 and 2 areinterconnected by means of the diagonal cross-element 6 at their bottomportions, the respective ends of the cross-element 6 actually beingconnected to the corresponding prop sockets 12 and 14 in which props 1and 2 are supportingly received, respectively. In like manner, props 3and 4 are interconnected by the diagonal crosselement 7, thecross-element 7 actually connecting the corresponding prop sockets 13and 15 at the lower ends of the respective props and into which thelower ends of the props are supportingly received.

A piston-cylinder arrangement is used as moving means for advancing theprops in the longitudinal direction including a cylinder 5 and adouble-acting piston (not shown) disposed on the piston rod 11 foroperable actuation within cylinder 5. The ends of piston rod 11 extendoutwardly through the corresponding ends of the cylinder 5 in the wellknown manner. Accordingly, upon passing pressure fluid to the cylinder 5on one side of the piston (not shown), the cylinder and piston will moverelative to one another in one direction and upon passing pressure fluidto cylinder 5 on the other side of the piston (not shown) movement inthe opposite direction will be achieved. Double acting piston-cylinderarrangements are well known and their operation simple. Therefore, unduedescription of this conventional arrangement is not necessary to a clearunderstanding of the inventive features of the instant arrangement.

Cross-element 6 is positioned over cross-element 7 with thecross-portions in abutting sliding relationship. The axis of cylinder 5bisects the cross-portions of elements 6 and 7. Advantageously, a clampstrap 8 is secured onto the top surface of cross-element 6, clamp strap8 being provided with an intermediate upward arcuate portion definingwith the corresponding portion of the cross-element 6 a seating channelextending in the in fixed relation thereat.

longitudinal direction for receiving a portion of cylinder Accordingly,the correspond ing portion of the cross-element 6 is slightly downwardlyarcuately depressed (see FIG. 2) in the longitudinal direction so as toform a tight fit for cylinder 5 as well as a guide rail on the underside thereof. Correspondingly, the central or cross-portion of theunderlying crosselement 7 is slightly downwardly arcuately depressed inthe longitudinal direction (see FIG. 2) in order to form a correspondingguide track on the upper side thereof. In this manner, the slidingabutment between the crosselements may be carried out in coactingguiding relation to preserve the longitudinal disposition of thepistoncylinder arrangement and the longitudinal forward and rearwarddirection of movement of the prop set including props 1 and 2, on theone hand, and the prop set including props 3 and 4, on the other hand.

While props 1 and 2 are connected with cylinder 5 for simultaneousmovement therewith, by reason of the fact that their interconnectingcross-element 6 is fixedly secured to cylinder 5, in the case of props 3and 4, the interconnecting cross-element 7 is not connected with thepiston rod 11, but merely slides under cross-element 6. In order toeffect the movement of props 3 and 4, resilient leaf spring connectors 9and 10 are provided, respectively, these connectors extendingtransversely medially to the outer ends of piston rod 11 for connectiontherewith. While strap 9 extends to the corresponding end of piston rod11 from a point close to the center of prop 3, in order to achieve adesirably large amplitude stroke for the piston rod 11, prop socket 15for the prop 4 is rearwardly extended a desired distance, wherebyconnector 10 may connect prop 4 with rod 11 in a convenient way.

Of course, by providing props 1 and 2 of the first diagonal frame propset in disengaged condition with the mine ceiling and mine floor whileproviding props 3 and 4 of the second diagonal frame prop set inengagement with the mine ceiling and mine floor, the first frame propset may be advanced in the longitudinal direction by merely passsingfluid to cylinder 5. During the forward movement, diagonal cross-element6 will slide along the guide track provided in diagonal cross-piece 7therebelow. Assuming that this action has taken place, the props will bein the position shown in FIG. 1.

Thereafter, by placing props 1 and 2 of the first frame prop set inengagement with the 'mine ceiling and mine floor, and disengaging props3 and 4 from engagement, props 3 and 4 may be advanced to the positionshown in phantom in the direction of arrows by passing hydraulic fluidto the opposite cylinder chamber. During this time, piston rod 11 willmove relative to the now stationary cylinder 5 and by reason of theconnectors 9 and 10, piston rod 11 will carry forward props 3 and 4 inthe desired manner. It will be appreciated that the intermediatediagonal cross-element 7 serves to provide greater stability for thediagonal frame prop set 3, i, such cross-element 7 not only improvingthe connection between props 3 and 4 but also stabilizing thepositioning of the first prop frame set 1, 2 by reason of the abuttingportions between cross-elements 6 and 7.

In accordance with the preferred embodiment, the props of at least onediagonal frame prop set are dis placeably positioned within therespective prop sockets therefor in order to permit slight pivotaldisplacement of the sockets about the prop bottom ends as pivot point.

As may be appreciated from FIG. 3, the diagonal crosselements 6, 7 andconnectors 9, 10 are disposed at the lower end of the arrangement withcylinder 5 and piston rod 11 disposed slightly above the mine floor byreason of the dimensions of the prop sockets or bases 13, 14, forexample. By making cross-elements 6, 7, and connectors or straps 9, 10of resilient leaf spring material, unevenness in the mine floor and mineceiling will be readily accommodated without undue stress on the workingparts, and moreover, the piston-cylinder arrangement may sag slightlyinto contact with the floor to further provide an intermediatestabilizing support. As shown, prop 2 is directly in front of prop 4while prop 3 is directly in front of prop 1, the positional relationshipbeing the same as indicated in FIG. 1. The props are shown as adjustablepit props of conventional design similar to the construction ofhydraulic jacks.

At the upper ends of props 2 and 3, overhead supporting caps 16 and 17,respectively, are provided, while correspondingly, at the upper ends ofprops 4 and 1, overhead supporting caps 18 and 19, respectively, areprovided. It will be appreciated, in this connection, that while prop 2is diagonally connected with prop 1 and prop 3 is, in turn, diagonallyconnected with prop 4, by reason of the crosselements 6 and 7, cap 16 ofprop 2 is connected on the same side of the piston-cylinder arrangementwith cap 17 of prop 3 whereas cap 18 of prop 4 is connected on the sameside with cap 19 of prop 1. Hence, while diagonal connections areachieved at the bottoms of the props, parallel longitudinal connectionsare achieved at the tops of the props.

Specifically, the longitudinally extending prop on each side of thepiston-cylinder arrangement are interconnected by an overhead capadjustable length linkage means including a pair of parallel middlelinkage bars 24, each pivotally connected at its respective ends tocorrespondingly positioned lateral linkage bars 24' (see FIG. 4). Inturn, the outer ends of the three lateral linkage bars 24', on eitherside of the middle bars 24, are connected with the respective ends ofthe overhead supporting caps of the props. Thus, caps 16 and 17, on theone hand, and caps 18 and 19, on the other hand, may be extended andretracted advantageously, within the limits provided by the particularconstructional lengths of the intermediate linkage means.

In operation, prop 2 will move longitudinally forward in the directionof arrow 25 as shown in FIG. 3 together with prop 1 diagonallypositioned with respect thereto. Since the cap of prop 2 during thistime would be connected with the stationary cap 17 of prop 3 on the sameside of the piston-cylinder arrangement and since cap 19 of prop 1 wouldbe connected with cap 18 of the stationary prop 4, the linkage means andcap lengths of the arrangement must be properly dimensioned inconjunction with the maximum amplitude stroke of the piston to preservethe desired functional relationship. For this purpose, the distance abetween the center point of prop 4 and the outermost pivot point 22 ofthe corresponding cap 18 plus the distance b between the center point ofprop 1 and the outermost pivot point 23 of the corresponding cap 19 mustbe shorter than the distance c between the center point of prop 2 andthe pivot point 20 at the outermost end of cap 16 plus the distance dbetween the center point of the prop 3 and the outermost pivot point 21of the corresponding cap 17. This is shown schematically in FIGURE 3best by the distance between the pivot points 22 and 23 of caps 18 and19, when the linkage is extended, as opposed to the distance between thepivot points 215 and 21 of caps 16 and 17 where the linkage isretracted.

Considering the illustrations of FIGURES 3 and 4, upon actuation of thepiston cylinder arrangement, props 4 and 3 will be advanced in thedirection of arrow 25 whereby the linkage between stationary cap 16' andadvancing cap 17 will be extended while the linkage between moving cap18 and stationary cap 19 will be retracted.

Such retraction is limited by the distance apart of pivot points 22 and23, since a short distance apartwill necessitate short strokes of thepiston cylinder arrangement or else the outer end of cap 18 will abutagainst the co r V other hand, as aforesaid, due to the shorter distancea and b, the corresponding ends of caps 18 and 19 will not undesirablyabut one another, so long as the stroke amplitude of the piston-cylinderarrangement is adjusted accordingly.

Considering the over-all operation of conventional mining framearrangements as contrasted with the arrangement in accordance with theinvention, FIG. illustrates that the frame pairs used in the prior artwere positioned for parallel movement with the piston attached to oneframe unit and the cylinder attached to the other frame unit. Thus, theleft-hand side frame unit had to be disengaged from the mine ceiling andmine floor for advancing, and upon engagement with the mine ceiling andmine floor, the right-hand frame unit could be disengaged foradvancement in its turn. However, either the left side or the right sideof each frame arrangement had to be disengaged for advancement leavingmore than one-half of the surface area to be supported in a condition ofnon-support.

Turning to FIGURE 6, a similar plurality of frame units is provided, butin this case the overhead caps are movable in accordance with theinvention. Thus, the forward left-hand side cap moves simultaneouslywith the rearward right-hand side cap along the line of units so that agreater degree of distribution of the support will be achieved in aneven manner. Considering the weight of the overhead seam to besupported, the type of operations involved, the size of the miningequipment, the area occupied by each frame unit, and the actual areasupported when one or both frame units are in engagement with the mineceiling as opposed to the entire surface of the mine ceiling, theadvantages of the diagonal frame positioning of the invention becomeapparent.

Clearly, the unsupported surfaces of the overhead seam are diminished byat least one-half during the advancing of either of the frames, inaccordance with the invention, since these frames are diagonallyinterconnected. While a certain portion of the support of the overheadseam is lacking on both sides of the arrangement during the advancingoperation, this is compensated for by the advantage of a more uniformsupport for the overhead seam. Of course, by reason of the diagonalinterconnections between the props to form the diagonal frames and themanner in which these frames are attached to the longitudinallyextending piston-cylinder arrangement, an enlarged stability under loadof the entire arrangement is assured while the overhead caps aremaintained in parallel relation in the longitudinal direction. Asaforesaid, the length of the caps measured from the center point of therespective prop to the outermost point of the cap where the linkage orhinged joint is connected should be smaller in total than the combinedlengths between the center points of the props on the opposite side ofthe piston-cylinder arrangement and the outermost pivot points thereforfor connecting the linkage or hinged joint means. The increments ofshortness as aforesaid are measured by the length of the stroke of thepiston cylinder arrangement in operation to provide an unobstructedincrement of advance of one diagonal frame followed by the other.

It will be appreciated that by reason of the linkage means 24, 24, thedifference in length occasioned by the lowering of the caps out ofengagement with the mine ceiling is generally offset. While this isespecially true with respect to the longer distance cap linkage in bothpositions and to the shorter distance cap linkage in re tractedposition, a different situation obtains where the shorter distance caplinkage is in extended position. In the latter instance, since one ofthe caps is stationary vand in engagement with the mine ceiling whilethe cap measured by the outermost pivot point of the stationary cap andthe outermost pivot point of the cap being lowered from engagement. Inaccordance with the invention, the proper distance measured between thetwo pivot points may be effectively maintained without any prop tiltingwhere the shorter distance cap linkage means are in maximum extendedposition, by providing each of the shorter distance caps, preferably,with a wide cap socket into which the corresponding prop head issituated in a displaceable manner.

Specifically, where prop 1 is stationary and the linkage is in maximumextended position with respect to prop 4 which is released fromengagement with the mine ceiling, the distance between pivot 23 andpivot 22 may be maintained, with the multiple joint 24, 24' in suchextended position describing a circle about point 23 as center, withoutany tilting, by constructionally providing the upper ends of the props1, 4 with spherical heads for engaging corresponding spherical socketsin the respective caps, the diameter of the spherical prop heads beingslightly less than the diameter of the corresponding spherical capsockets. In this manner, a slight displacement of the caps on therespective props may take place in the direction of advance, i.e., as,for example, is Shown by arrow 25, so that the maximum limit of themultiple joint in extended position is compensated sufiiciently toprevent undesired tilting of the props.

In the case of shorter cap 18, therefore, while prop 4 may be lowered,cap 18 will be displaced both in downward direction with prop 4 and inforward direction on the prop head to maintain the fixed distancebetween pivot point 22 of cap 18 and pivot point 23 of cap 19 vialinkage 24, 24'. The opposite action will take place where prop 4 isstationary and prop 1 is released for advance.

This provision for slight displacement between the props and thecorresponding caps does not alter in any way the desired overheadsupport of the mine ceiling in view of the over-all arrangement inaccordance with the invention, but, in fact, avoids a loss of supportwhich might otherwise be occasioned by the tilting of the props out oftheir normal spherical position.

Nevertheless, it should be noted that the lower ends of the props 1, 2,3, 4 may be movably inserted, in the usual way, in the bottom sockets orbases 12, 13, 14, 15 to permit a desired degree of displacement toprevent undue stress on the working parts by unevenness in the minefioor.

What is claimed is:

1. Advanceable mining support arrangement with adjustable pit prop meansfor engaging the mine ceiling and mine floor, which comprises movingmeans having a forward and a rearward end and including a double-actingpiston-cylinder arrangement, first prop means positioned adjacent saidforward end on one side of said moving means and second prop meanspositioned adjacent said rearward end on the opposite side of saidmoving means, said first and second prop means together forming a propset and being connected with the piston of said moving means forsimultaneous forward and rearward movement, and third prop meanspositioned adjacent said forward end on said opposite side of the movingmeans and fourth prop means positioned adjacent said rearward end onsaid one side of said moving means, said third and fourth prop meanstogether forming a prop set and being connected with the cylinder ofsaid moving means for simultaneous forward and rearward movementalternately with the movement of said first and second prop means.

2. Arrangement according to claim 1 wherein the prop means of one setare interconnected by a first diagonal cross-element and the props ofthe other set are interconnected by a second diagonal cross-elementoverlying the first cross-element, the adjacent cross-portions of saidcross-elements being in sliding abutment with each other.

3. Arrangement according to claim 2 wherein said piston-cylinderarrangement includes a double-ended cylinder and a double-ended pistonrod extending through the corresponding ends of the cylinder, saidpiston and cylinder being arranged for actuation in forward and rearwarddirection with respect to one another, said cylinder beinglongitudinally disposed between'said first and fourth prop means on onesideand said third and second prop means on the opposite side, and saidcylinder being fixedly secured to the cross-portion of one of saiddiagonal crosselements to move the corresponding prop set while saidpiston rod is connected at each end with a corresponding prop means ofthe remaining set to move said set alternately with the movement of thecylinder.

'4. Arrangement according to claim 3 wherein the axis of said cylinderlongitudinally bisects the cross-portions of said diagonalcross-elements, said cylinder being fixedly secured to the top side ofthe overlying diagonal crosselement by a clamp strap extending in thedirection of and being substantially coextensively secured to saidcrosselement, said clamp strap having an intermediate upward arcuateportion defining with the corresponding portion of the cross-element aseating channel extending in the longitudinal direction for receiving atleast a portion of said cylinder in fixed relation thereat.

5. Arrangement according to claim 4 wherein the said correspondingportion of the overlying cross-element is slightly downwardly arcuatelydepressed in said longitudinal direction to form a guide rail on theunder side of said cross-element and in turn the corresponding portionof the cross-element underlying said overlying crosselement is alsoslightly downwardly arcuately depressed in said longitudinal directionto form a corresponding guide track on the upper side thereof, wherebythe sliding abutment between said cross-elements may be carried out incoacting guiding relation.

6. Arrangement according to claim 5 wherein each prop means has a lowerend an an upper end, the crosselements and piston rod being connected tosaid prop means at the corresponding lower ends, and said prop meanseach being provided with an overhead supporting cap at the upper end.

7. Arrangement according to claim 6 wherein said prop means are eachprovided with a prop socket in which the lower end of the prop means isremovably seated, said caps each having a cap socket and the upper endof each prop means having a'cap head, the width of said cap socket beingslightly greater than the width of the cap head therefor, whereby saidcap may be displaced slightly in the longitudinal direction with respectto the prop means therefor.

8. Arrangement according to claim 7 wherein the first and fourth propmeans on the same side of said moving means are longitudinallyinterconnected at their upper ends through their corresponding overheadcaps by an overhead cap adjustable length linkage and the third andsecond prop means on the opposite side of said moving means arelongitudinally interconnected at their upper ends through theircorresponding overhead caps by an overhead cap adjustable lengthlinkage, said linkages being adjustably dimensioned for permitting theset including the first and second prop means to move forward in thelongitudinal direction of advance While the set including the third andfourth prop means is stationary so that the cap linkage between thefirst and fourth prop means will increase in length while the caplinkage between the third and second prop means will decrease in length,and alternately for permitting the set including the third and fourthprop means to move forward in longitudinal direction of advance whilethe set including the first and second prop means is stationary so thatthe cap linkage between the first and fourth prop means will decrease inlength v while the cap linkage between the third and second prop meanswill increase in length.

9. Arrangement according to claim 8 wherein each said caplinkage'includes middle linkage bar means pivotally connected at eachbar end to lateral linkage bar means, each said lateral linkage barmeans being sepai'ately pivotally connected in turn to the substantiallyoutermost point of the corresponding overhead supporting cap, forextension and retraction in length of the corresponding linkage inlongitudinal direction in coaction with the forward movement of the propsets.

10. Arrangement according to claim 9 wherein the sum of the distancesbetween the center point of each of the two prop means interconnected byone of the cap linkages and the respective outermost point of thecorresponding overhead supporting cap therefor which is pivotallyconnected to the said one cap linkage is shorter than the sum of thedistances between the center point of each of the remaining two propmeans interconnected by the other of the cap linkages and the respectiveoutermost point of the corresponding overhead supporting cap thereforwhich is pivotally connected to the said other cap linkage, such shorterdistance being shorter by an increment equal to at least the maximumamplitude stroke of the piston in the said cylinder.

11. Arrangement according to claim 10 wherein said diagonalcross-elements are resilient flat leaf spring members, said piston rodbeing resiliently connected with the corresponding prop means thereforby resilient flat leaf spring connectors, and said prop means beinghydraulic pit prop means.

12. Advanceable mining support arrangement with adjustable height pitprops for engaging the mine ceiling and mine floor, which compriseslongitudinally extending motor means including a cylinder having aforward and a rearward end, a double acting piston mounted on a pistonrod operably disposed in said cylinder for relative forward and rearwardmovement, said rod having ends extending through the corresponding endsof the cylinder, four pit props, each having an overhead supporting cap,said props including first and fourth props positioned as a pair intandem on one longitudinal side of said cylinder and third and secondprops positioned as a pair in tandem on the other longitudinal side ofsaid cylinder, said first and fourth prop pair being longitudinallyparallel to said third and second prop pair and both said pairs beingparallel to said cylinder and rod, said first prop being positionedadjacent said forward end and said second prop being positioned adjacentsaid rearward end and being interconnected by a first resilient flatleaf spring diagonal cross-element with the cylinder to form a firstprop set for simultaneous forward and rearward movement with themovement of said cylinder, correspondingly said third prop means beingpositioned adjacent said forward end and said fourth prop beingpositioned adjacent said rearward end and being interconnected by asecond resilient fiat leaf spring diagonal cross-element to form asecond prop set, said second cross-element extending cross-wiseunderneath the first cross-element in sliding engagarnent therewith,said third and fourth props each being connected to a corresponding endof. said rod by a transversely medially extending resilient flat leafspring connector for simultaneous forward and rearward movement of saidsecond prop set with the movement of said rod alternately with themovement of said first prop set together with the movement of saidcylinder, the axis of said cylinder longitudinally bisecting thecross-portions of said cross-elements, a clamp strap extending in thedirection of and being substantially coextensively secured onto theupper side of the first cross-element, said strap having an intermediateupward arcuate portion defining with a corresponding portion of saidfirst cross-element a seating channel extending in the longitudinaldirection receiving partly and fixedly securing therewithin saidcylinder, said corresponding portion of the first cross-elernent beingslightly downwardly arcuately depressed in said longitudinal directionto form a guide rail on the under side of said first cross-element andin turn the corresponding portion of the second cross-element thereunderbeing also slightly arcuately depressed in said longitudinal directionto form a corresponding guide track on the upper side thereof, wherebysliding abutment between said crosselements may be carried out incoacting guiding relation, the first and fourth props beinglongitudinally interconnected at their upper ends through theircorresponding overhead caps by an adjustable length first linkage andthe third and second props being longitudinally interconnected at theirupper ends through their corresponding overhead caps by an adjustablelength second linkage, said linkages being adjustably dimensioned forpermitting the set including the first and second props to move forwardin the longitudinal direction of advance while the set including thethird and fourth props is stationary so that the first linkage betweenthe first and fourth props will increase in length While the secondlinkage between the third and second props will decrease in length andalternately for permitting the set including the third and fourth propsto move forward in the longitudinal direction of advance while the setincluding the first and second props is stationary so that the firstlinkage between the first and fourth props will decrease in length whilethe second linkage between the third and second props will increase inlength.

13. Arrangement according to claim 12 wherein each said cap linkageincludes middle linkage bar means pivotally connected at each bar end tolateral linkage bar means, each said lateral linkage bar means beingseparately pivotally connected in turn to the substantially outermostpoint of the corresponding overhead supporting cap, for extension andretraction in length of the corresponding linkage in longitudinaldirection in coaction with the forward movement of the prop sets.

14. Arrangement according to claim 13 wherein the sum of the distancesbetween the center point of each of the two props interconnected by saidfirst linkage and the respective outermost point of the correspondingcap therefor which is pivotally connected to said first linkage isshorter than the sum of the distances between the center point of eachof the remaining two props interconnected by said second linkage and theoutermost point of the corresponding cap therefor which is pivotallyconnected to said second linkage, by an increment equal to the amplitudestroke of the piston in the said cylinder.

15. Arrangement according to claim 14 wherein each said prop is providedat its upper end with a cap head and each said overhead cap is providedwith a cap socket, the width of said socket being greater than the widthof said head, whereby longitudinal displacement of each said cap withrespect to the corresponding prop may take place when one cap is loweredfrom engagement with the mine ceiling while the cap linkably connectedtherewith remains in engagement with the mine ceiling, and each saidprop having at its lower end a base socket, the lower end of the propbeing movably inserted in the base socket.

References Cited by the Examiner FOREIGN PATENTS 1,229,479 3/60 France.

EARL J. WITMER, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

1. ADVANCEABLE MINING SUPPORT ARRANGEMENT WITH ADJUSTABLE PIT PROP MEANSFOR ENGAGING THE MINE CEILING AND MINE FLOOR, WHICH COMPRISES MOVINGMEANS HAVING A FORWARD AND A REARWARD END AND INCLUDING A DOUBLE-ACTINGPISTON-CYLINDER ARRANGEMENT, FIRST PROP MEANS POSITIONED ADJACENT SAIDFORWARD END ON ONE SIDE OF SAID MOVING MEANS AND SECOND PROP MEANSPOSITIONED ADJACENT SAID REARWARD END ON THE OPPOSITE SIDE OF SAIDMOVING MEANS, SAID FIRST AND SECOND PROP MEANS TOGETHER FORMING A PROPSET AND BEING CONNECTED WITH THE PISTON OF SAID MOVING MEANS FORSIMULTANEOUS FORWARD AND REARWARD MOVEMENT, AND THIRD PROP MEANSPOSITIONED ADJACAENT SAID FORWARD END ON SAID OPPOSITE SIDE OF THEMOVING MEANS AND FOURTH PROP MEANS POSITIONED ADJACENT SAID REARWARD ENDOF SAID ONE SIDE OF SAID MOVING MEANS, SAID THIRD AND FOURTH PROP MEANSTOGETHER FORMING A PROP SET AND BEING CONNECTED WITH THE CYLINDER OFSAID MOVING MEANS FOR SIMULATANEOUS FORWARD AND REARWARD MOVEMENTALTERNATELY WITH THE MOVEMENT OF SAID FIRST AND SECOND PROP MEANS.